plugins or addons that add more nodes?
I would suggest looking up Open Shading Language (OSL). There are a number of repos using it available on Github.

To use it, you'll need to be using Cycles (Eevee, in the interest of being fast, does not support OSL at this time). Additionally, you'll need to be rendering on your CPU, not your GPU; while it's possible in theory, no one has implemented OSL rendering on the GPU yet and it's no small undertaking.

After you have that set up on your Render context, you'll want to select the checkbox for "Open Shading Language". This prepares Blender to run its internal OSL interpreter.

After that, in your shader, you'll have a Script node available. Add one. It seems simple at first; you just have a box for the OSL file and a toggle for a file-internal vs. file-external location; assuming you've got an OSL, click external, and open it up in the box. Once your OSL is open, the script node will have a lot more character, along with (presumably) some new inputs and outputs. Hook them up, play with your new node!

I hope that helps.